Simulation of a hump structure in the optical scattering rate within a generalized Allen formalism and its application to copper oxide systems

Abstract: We propose a possible way to simulate a hump structure in the optical scattering rate. The optical scattering rate of correlated charge carriers can be defined within an extended Drude model formalism. When some electron and hole doped copper oxide systems are in the spin density or charge density wave phases they show hump structures in their optical scattering rates. The hump structures have not yet been simulated and understood clearly. We are able to simulate the hump structure by using a peak followed by a dip feature in the normalized density of states within a generalized Allen formalism. We observe that reversing the order of the dip and peak gives completely different features in the optical scattering rate; a peak-dip (dip peak) results in a hump (a valley) in the scattering rate. We also obtain the real part of the optical conductivity and reflectance spectra from the simulated optical scattering rate and compare them with published experimental spectra. From these comparisons we conclude that the peak-dip order can give the hump structure, which is observed experimentally in copper oxide systems. Finally we fit two published optical spectra with our new model and discuss our results and the possible origin of the dip or peak features in the normalized density of states.